As a technology to implement new communication tools in the wake of voice communication using mobile terminals and TV telephone communication, a PoC (Push-to-Talk Over the Cellular) server, disclosed in Non-patent Document 1, for example, is known. A PoC server implements a 1 to N communication service, which allows simultaneous voice communication from a user of one mobile terminal, who presses the call button, to other users of a plurality of mobile terminals based on a packet exchange type best effort voice service.
Non-patent document 1: Naomasa Yoshida, Masaharu Nakagawa, Makoto Nakayama, Yohei Inokai, Miya Matsuda, Masanobu Yamagiwa: “System develop for push talk service”, NTT DoCoMo Technical Journal, Vol. 13, No. 4, pp. 6 to 13, Jan. 1, 2006